Am I off my rocker? COAL and OGIVE

[rammac]

Okay, so I am about a year into reloading. Gotten a few loads worked up and I feel like I am throwing darts and a few stick. Basically, loading up .5 grain diff. shooting groups and staying within factory recommended COAL, but have played with seating depth a little.

Working a 6.5 CM. It is a CVA Cascade and it is really an accurate rifle. Lucked into a super accurate load, but it was one of my first ones and realized my calculations were off and I was overpressured, as I was setting the scope for deer season and I was getting bolt resistance. Came back and checked my numbers and the way I calculated, well, it was a novice way of doing things when you don't have the powder listed. lesson learned.

So, a buddy sent me a video and been doing some measurements to get .020 off lands as a starting point. What i found freaked me out a little. Two bullets - 140 Nosler Accubond (COAL 2.805) and Norma Bondstrike (COAL 2.803). Here is what I found...

Nosler measurement for OAL into lands is 2.790.
Norma measurement for OAL into lands is 2.880.
Nosler measurement to Ogive into lands is 2.272.
Norma measurement to Ogive into lands is 2.260.
Nosler bullet length 1.358.
Norma bullet length 1.408.

So, given this information, the Ogive is only about .012 difference in the two. However, with them using nearly the same COAL for bullets that have quite different length measurement, one is being jammed into the lands (Nosler) while the other has about .075 jump from the lands (Norma).

So, would it be prudent to measure .20 off lands using Ogive (.020 off lands was the recommendation from the video, and making .003 incremental changes to tighten groups), which is going to give me way different COAL than the manufacturers recommendation?

Am I off my rocker?

First of all, I don't understand how your Nosler OAL is less than the recommended length of 2.80". That tells me that you are doing something wrong when you measure things. Are you measuring the distance to the lands using a tool or a loosely seated bullet?

 

[USAFRet]

First of all, I don't understand how your Nosler OAL is less than the recommended length of 2.80". That tells me that you are doing something wrong when you measure things. Are you measuring the distance to the lands using a tool or a loosely seated bullet?

I used the Hornady OAL gauge to check the chamber of my rifle where the 140 Accubond meets the lands. When I did this check, the OAL of the case and bullet was 2.790. Which means that the recommended 2.805 would be jamming the bullet into the lands.

 

[USAFRet]

In short the hand loading process is as deep and wide as you want it to be. Shooters from as far back as their beginning days of hand loading will tell you the rabbit hole never ends.

I am learning that the rabbit hole likes to suck money in. Haha.

 

[USAFRet]

Now that you've measured bullets, you shud be able understand how there can be so much variance in OAL's, and that OAL is really only applicable to the mag length. The CBTO ( cartridge base to ogive) is the length that really counts, and the bullets also illustrate how that can change, then you get different guns, they will change again. Welcome to the mad, mad world of reloading and guns.

Thanks, Jones. This was a lightbulb moment for me. That point where you see people talking about this stuff and you don't quite get it. Then you run into it and bingo.

 

[6Creed73]

I used the Hornady OAL gauge to check the chamber of my rifle where the 140 Accubond meets the lands. When I did this check, the OAL of the case and bullet was 2.790. Which means that the recommended 2.805 would be jamming the bullet into the lands.

I agree with rammac on this. I've never seen a recommended OAL be jammed. You may just want to double check the measurement for that bullet with your OAL gauge. Make sure the case is seated in the chamber as far as it can before pushing the bullet forward.

 

[William Vogel]

Thanks! So, the scary part is that .020 off lands for the Norma has me at 2.860 OAL vs 2.803 as recommended. That is huge.

That’s not huge. That’s .057. Here’s a picture of my 223 bolt action load vs nearly every load in a reloading manual (2.25). Mine measures 2.65. You have to find what the gun likes and keep the pressure within safety. My load is a 75 grain bullet running 2980fps and it’s below 55,000 psi.

 

[Bill Norris]

That’s not huge. That’s .057. Here’s a picture of my 223 bolt action load vs nearly every load in a reloading manual (2.25). Mine measures 2.65. You have to find what the gun likes and keep the pressure within safety. My load is a 75 grain bullet running 2980fps and it’s below 55,000 psi.
View attachment 1468058

Reinforcing the fact. The ogive measurements in comparison will be much closer between two different bullets than COL measurements.

 

[USAFRet]

I agree with rammac on this. I've never seen a recommended OAL be jammed. You may just want to double check the measurement for that bullet with your OAL gauge. Make sure the case is seated in the chamber as far as it can before pushing the bullet forward.

Quadruple checked it and pressed it in as hard as I could. Same each time. It is a CVA Cascade.

 

[William Vogel]

Quadruple checked it and pressed it in as hard as I could. Same each time. It is a CVA Cascade.

Apparently your chamber isn’t the same spec chamber as what Nosler tested. The Norma bullet appears to be secant ogive and the Nosler is hard to tell but it’s much more of a tangent ogive or a hybrid. I’m only looking at pictures. My 6.5 Creedmoor was really close to the lands at 2.800 COL with Hornady 147ELD before I lengthened the freebore.
What you’ve done is exactly what is needed to establish the chamber dimensions of your rifle. I rented the precision reamer from 4DReamer Rental and modified my chamber. The reason I lengthened my freebore was to get the bearing surface of the bullet out of the body of the case and only in the neck. I did this because I don’t want any contact of the bullet into what’s known as the donut if it developed into my cases. The increased case volume also allows a little more powder and velocity. Unfortunately I didn’t hit another accuracy point before I saw pressure and I backed off.

 

[K22]

The very first thing I do when I start reloading for a new rifle or new bullet is measure the max COL base to ogive contact with the lands for that bullet in that rifle. Therefore, there is no guess work. I usually measure 3 bullets and use the lowest one. I use a version of the Frankfort Arsenal tool to make the measurements. I believe this is very important.

The problem with using manufacturer's tested COL is that it may not be optimum for your rifle or worse, cause a significant jam. For example, Sierra list a COL of 2.650 for the 6mm 85 grain BTHP. That will chamber with no problem in my Remington 700 but will cause a severe jam in my Tikka and Browning X bolt. So bad, that the bullet will stick in the lands when ejecting the cartridge. Firing such a cartridge would not be a good thing.

Secondly, for hunting bullets, some variation of ogive is quite normal thus by seating at least .020" off the lands you assure yourself that you won't end up with a bullet stuck in the lands when ejecting an unfired cartridge or worse, cause a potentially dangerous pressure surge.

For a hunting rifle, reliability is just as important as accuracy. You have to have reliable reloads that will chamber and extract without issue. You don't need to load like the competition benchrest shooters and try to squeeze a few thousands in group size reduction as the risk of compromising reliability.

If you want to play around with seating depth to optimize the load for your rifle, that's fine just make sure the cartridge will fit the magazine and the bullet will be off the lands a sufficient amount to account for variations in bullet ogives even without the same lot.

 

[USAFRet]

Reinforcing the fact. The ogive measurements in comparison will be much closer between two different bullets than COL measur

Apparently your chamber isn’t the same spec chamber as what Nosler tested. The Norma bullet appears to be secant ogive and the Nosler is hard to tell but it’s much more of a tangent ogive or a hybrid. I’m only looking at pictures. My 6.5 Creedmoor was really close to the lands at 2.800 COL with Hornady 147ELD before I lengthened the freebore.
What you’ve done is exactly what is needed to establish the chamber dimensions of your rifle. I rented the precision reamer from 4DReamer Rental and modified my chamber. The reason I lengthened my freebore was to get the bearing surface of the bullet out of the body of the case and only in the neck. I did this because I don’t want any contact of the bullet into what’s known as the donut if it developed into my cases. The increased case volume also allows a little more powder and velocity. Unfortunately I didn’t hit another accuracy point before I saw pressure and I backed off.

That makes perfect sense. I appreciate the input. I really don't want to mess with the rifle too much. It is very accurate. I am just running my load back .020 off the lands and will see how that does. I left the Norma to spec as I was getting good accuracy. I just had to back down off the most accurate load due to pressure issues.

This was the Norma 143 yesterday with H-4350. Wish I wasn't having the pressure issues.

 

[USAFRet]

The very first thing I do when I start reloading for a new rifle or new bullet is measure the max COL base to ogive contact with the lands for that bullet in that rifle. Therefore, there is no guess work. I usually measure 3 bullets and use the lowest one. I use a version of the Frankfort Arsenal tool to make the measurements. I believe this is very important.

The problem with using manufacturer's tested COL is that it may not be optimum for your rifle or worse, cause a significant jam. For example, Sierra list a COL of 2.650 for the 6mm 85 grain BTHP. That will chamber with no problem in my Remington 700 but will cause a severe jam in my Tikka and Browning X bolt. So bad, that the bullet will stick in the lands when ejecting the cartridge. Firing such a cartridge would not be a good thing.

Secondly, for hunting bullets, some variation of ogive is quite normal thus by seating at least .020" off the lands you assure yourself that you won't end up with a bullet stuck in the lands when ejecting an unfired cartridge or worse, cause a potentially dangerous pressure surge.

For a hunting rifle, reliability is just as important as accuracy. You have to have reliable reloads that will chamber and extract without issue. You don't need to load like the competition benchrest shooters and try to squeeze a few thousands in group size reduction as the risk of compromising reliability.

If you want to play around with seating depth to optimize the load for your rifle, that's fine just make sure the cartridge will fit the magazine and the bullet will be off the lands a sufficient amount to account for variations in bullet ogives even without the same lot.

Excellent information and advice. That sounds like the same issue I am having, so maybe I am not off my rocker. Thank you.

I have been all over the map on reloading. I am going to slow down and focus on one or two rifles and get them nailed down using the chamber gauge and ladder testing. Yeah, I got a few rifles and worse, I have another one being built. My first, no kidding, custom build (aside from an old Air Force buddy that builds AR-15 uppers with his own barrels for me...and they are tack drivers). This one is a 7mm-08 with a Carbon 6 barrel and a Mack Bros EVO II action. I will use your approach right off the bat. Thanks.

 

[Coyotefurharvester]

Something to remember, typically there will be more than one "best" seating depth AND more than one charge weight(within the recommended range) that will produce possibly the best groups for an individual barrel. Monolithic bullets tend to show a "jump" accuracy node(0.050+), and when loading for hunting rds manufacturer suggested lengths will be reliable ammo. Reliability being chamber and extract easily, and safely. And deer wouldn't know if your starting a load at 2600 or 2800.

 

[K22]

Excellent information and advice. That sounds like the same issue I am having, so maybe I am not off my rocker. Thank you.

I have been all over the map on reloading. I am going to slow down and focus on one or two rifles and get them nailed down using the chamber gauge and ladder testing. Yeah, I got a few rifles and worse, I have another one being built. My first, no kidding, custom build (aside from an old Air Force buddy that builds AR-15 uppers with his own barrels for me...and they are tack drivers). This one is a 7mm-08 with a Carbon 6 barrel and a Mack Bros EVO II action. I will use your approach right off the bat. Thanks.

Good idea, slow down, master the basics first; safe and reliable reloads. Keep it simple and it will be more fun, at least it's that way for me.

Reloads for hunting can be rather straight forward, especially for big game. Bullet selection with regards to terminal performance is more important than tack driving accuracy. Today, the bullets available are far superior with in accuracy potential and terminal performance to the ones I started with a half a century ago.

By all means fine tune with varying powder charges but remember, for big game, the vital area is quite large. A reload than can produce a consistent 1 1/2 moa is more than adequate.

 

[KMart]

I am learning that the rabbit hole likes to suck money in. Haha.

Rabbits like to eat green stuff. In this case, MONEY

 

[USAFRet]

Good idea, slow down, master the basics first; safe and reliable reloads. Keep it simple and it will be more fun, at least it's that way for me.

Reloads for hunting can be rather straight forward, especially for big game. Bullet selection with regards to terminal performance is more important than tack driving accuracy. Today, the bullets available are far superior with in accuracy potential and terminal performance to the ones I started with a half a century ago.

By all means fine tune with varying powder charges but remember, for big game, the vital area is quite large. A reload than can produce a consistent 1 1/2 moa is more than adequate.

I am stuck on the bonded bullets, except for smaller calibers like my 223 and Grendel. More of a ballistic tip with them.

 

[USAFRet]

Something to remember, typically there will be more than one "best" seating depth AND more than one charge weight(within the recommended range) that will produce possibly the best groups for an individual barrel. Monolithic bullets tend to show a "jump" accuracy node(0.050+), and when loading for hunting rds manufacturer suggested lengths will be reliable ammo. Reliability being chamber and extract easily, and safely. And deer wouldn't know if your starting a load at 2600 or 2800.

"And deer wouldn't know if your starting a load at 2600 or 2800" Truth.

I just want accuracy and enough velocity to ethically take the animal. Anything MOA and below is good to go for me. Gas guns, only to 200 or 250, I can accept 1.5 MOA.

 

[Schippergreg]

That makes perfect sense. I appreciate the input. I really don't want to mess with the rifle too much. It is very accurate. I am just running my load back .020 off the lands and will see how that does. I left the Norma to spec as I was getting good accuracy. I just had to back down off the most accurate load due to pressure issues.

This was the Norma 143 yesterday with H-4350. Wish I wasn't having the pressure issues.

View attachment 1468085

I don’t believe that you stated what powder charge you were at when you seen pressure signs but I would keep your seating depth and drop a half grain to start, then test in
.3 less increments.

 

[rocketron]

What is the case head to shoulder measurement on the Hornady tool case and what is the same measurement on a fired case with primer removed?

 

[Newhouse]

OP, light reading material. https://bergerbullets.com/shoot-bet...actice in,optimal seating depth for precision.